Metal tube float flowmeter

two, principle:
The LZ series consists of two parts:
Sensor—measuring tube and float;
Signal transmitter - indicator
There are four kinds of liquid contact materials for sensors: stainless steel, Hastelloy, titanium, and stainless steel lining . Users can meet the pressure resistance and medium anti-corrosion requirements of the process according to different liquid contact materials. According to different measurement requirements, users can choose different indicator combinations to achieve different measurement requirements when selecting. The flow is measured by the transmitter in the indicator through the coupled magnetic steel to sense the change in the position of the float to complete the flow indication and the far-distance transmission of the signal. When the measured medium flows through the measuring tube from bottom to top, the float is balanced by the force of gravity, buoyancy and fluid velocity on the vertical upward direction of the float. The float is relatively stationary at a certain position, this position follows the float and the cone. The ring area of ​​the tube and the fluid flow rate change, and the position of the float corresponds to the flow rate of the measured medium.

Third, the characteristics
â—‡Modular combination design, easy maintenance, maintenance-free maintenance
â—‡Single-axis, non-contact new magnetic coupling structure, signal transmission is more stable
â—‡Two-line, large-screen LCD display instantaneous, cumulative flow, with backlight
â—‡Intelligent with power-down protection, data backup and recovery
â—‡All metal structure, anti-vibration, pressure resistance, temperature resistance, anti-corrosion
â—‡ Short stroke, 250mm main, easy to design and install

four, Technical Parameters
Measuring range: water (20 °C) 1-200000 l / h air (20 ° C, 0.1013MPa) 0.03-4000m3 / h See flow meter, special flow can be customized
Range ratio: standard type 10:1 special type 20:1
Accuracy: Standard type 1.5 special type 1.0 level
Pressure rating: Standard type: DN15-DN50 4.0MPa DN80-DN200 1.6MPa
Special type: DN15-DN50 25MPa DN80-DN200 16MPa
The pressure rating of the jacket is 1.6MPa
Special models should be negotiated with the factory before selection and ordering
Pressure loss: 7kPa-70kPa
Medium temperature: Standard type: -80 °C - +200 °C: PTFE: 0 °C - 85 °C
High temperature type: zui high up to 400 ° C
Medium viscosity: DN15: <5mPa.s (F15.1-F15.3)
<30mPa.s (F15.4-F15.8)
DN25: <250mPFa.s
DN50-DN150: <300mPa.s
Ambient temperature: liquid crystal type -30°C-+85°C
Pointer type -40 ° C - + 120 ° C
Connection form: standard type: DIN2501 standard flange
Special type: any standard flange or thread specified by the user
Cable interface: M20*1.5
Power supply: standard 24VDC two-wire system 4-20mA (10.8VDC-36VDC)
AC type: 85-265VAC 50HZ
Battery type: 3.6V@4AH nickel-metal hydride battery
Alarm output: upper or lower limit instantaneous flow alarm
Standard type: open collector output (zui large 100mA@30VDC internal impedance 100 ohms)
Special type: relay output (contact capacity zui large 5A@250VAC)
Pulse output: cumulative pulse output, zui small interval 50 ms
LCD display: instantaneous flow display value range: 0-50000
Cumulative flow display value range: 0-99999999
Protection level: IP65
Explosion-proof mark: intrinsic safety type iaIICT6 flameproof dIICT6

Detection principle:
The detecting portion is composed of a vertical conical tube which is expanded from the bottom to the top and a float which is freely movable up and down along the conical tube axis. The working principle is shown in Figure 1. When the measured fluid passes from the bottom to the annulus formed by the cone and the float, the differential pressure at the upper and lower ends of the float forms the force of the rise of the float. When the float is subjected to a greater force than the float in the fluid. At the weight, the float rises, the annulus area increases, the fluid flow rate at the annulus decreases immediately, the differential pressure at the upper and lower ends of the float decreases, and the lift force acting on the float decreases, until the rising force is equal to the float in the fluid. At the weight, the float is stable at a certain height. The height of the float in the cone is corresponding to the flow through.
The basic equation for volumetric flow Q is:
The flow coefficient of the α meter in the equation varies depending on the shape of the float;
ε The coefficient of gas expansion when the measured fluid is a gas, usually ignored due to the small amount of correction of the coefficient, and it has been included in the flow coefficient by calibration, such as liquid ε = 1
â–³F circulation annular area, m2;
g local gravity acceleration, m/s2;
Vf float volume, if extended, should also include, m3;
Ρf float material density, kg/m3;
ρ the density of the measured fluid, such as the density of the gas in the cross section upstream of the float, kg / m3;
Cross section of the Ff float working diameter (zui large diameter), m2;
Gf float weight, kg.
The relationship between the circulation annular area and the height of the float is as shown in equation (3). When the structural design has been determined, d and β are constant.
In the formula, there is a quadratic term of h. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is small, it can be regarded as approximate linear.

Where d floats zui large diameter (ie working diameter), m;
h The float from the inner diameter of the cone is equal to the height from the large diameter of the float zui, m;
The taper angle of the beta cone;
a, b is a constant
It can be seen from the formulas (1), (2), and (3) that under certain conditions, the height of the float in the cone tube has a certain proportional relationship with the volume flow. By reading the height of the float, you can know the corresponding volume flow, and then convert the height of the float to the scale corresponding to the corresponding volume flow through the converter. This is the detection principle.
Conversion indicator
The converter actually converts the height of the float in the cone into a scale of the corresponding volume flow. From the output signal: there is a local display
Display and remote signal output type:
In-situ display type: the rotation of the follower magnet in the local indicator and the magnetic steel in the float, and the electric pointer indicates the flow at this time through the dial

Intelligent remote transmission type , which is coupled with the magnetic steel in the intelligent indicator and the magnetic steel in the float, and rotates, and simultaneously drives the sensing magnet and the pointer, and converts the magnetic field change into an electrical signal through a magnetic sensor. /D conversion, digital filtering, microprocessor processing, D/A output, LCD liquid crystal display to show instantaneous flow and cumulative flow. (As shown below)

The flow coefficient of the α meter in the equation varies depending on the shape of the float;
ε The coefficient of gas expansion when the measured fluid is a gas, usually ignored due to the small amount of correction of the coefficient, and it has been included in the flow coefficient by calibration, such as liquid ε = 1
â–³F circulation annular area, m2;
g local gravity acceleration, m/s2;
Vf float volume, if extended, should also include, m3;
Ρf float material density, kg/m3;
ρ the density of the measured fluid, such as the density of the gas in the cross section upstream of the float, kg / m3;
Cross section of the Ff float working diameter (zui large diameter), m2;
Gf float weight, kg.
The relationship between the circulation annular area and the height of the float is as shown in equation (3). When the structural design has been determined, d and β are constant.
In the formula, there is a quadratic term of h. Generally, this nonlinear relationship cannot be ignored. Only when the cone angle is small, it can be regarded as approximate linear.

Where d floats zui large diameter (ie working diameter), m;
h The float from the inner diameter of the cone is equal to the height from the large diameter of the float zui, m;
The taper angle of the beta cone;
a, b is a constant
It can be seen from the formulas (1), (2), and (3) that under certain conditions, the height of the float in the cone tube has a certain proportional relationship with the volume flow. By reading the height of the float, you can know the corresponding volume flow, and then convert the height of the float to the scale corresponding to the corresponding volume flow through the converter. This is the detection principle.
Conversion indicator
The converter actually converts the height of the float in the cone into a scale of the corresponding volume flow. From the output signal: there is a local display
Display and remote signal output type:
In-situ display type: the rotation of the follower magnet in the local indicator and the magnetic steel in the float, and the electric pointer indicates the flow at this time through the dial

Intelligent remote transmission type , which is coupled with the magnetic steel in the intelligent indicator and the magnetic steel in the float, and rotates, and simultaneously drives the sensing magnet and the pointer, and converts the magnetic field change into an electrical signal through a magnetic sensor. /D conversion, digital filtering, microprocessor processing, D/A output, LCD liquid crystal display to show instantaneous flow and cumulative flow. (As shown below)

Calculation of caliber, float number and scale

1, calculation method
(1) According to the data given by the user, select the appropriate formula to calculate the flow Qs of the corresponding calibration medium:

Among them: Qs-calibration medium (water or air) flow under standard conditions (20 ° C, 0.1013 MPa)
Q-user media flow K-correction factor
(2) According to the calculated Qs value, check the flow meter to determine the selected float number and the diameter of the measuring tube (the values ​​in the flow meter are the flow values ​​of water or air in the standard state)
(3) After determining the diameter of the measuring tube and the float number, it is recommended to use the following formula to determine the upper limit value Q of the measured medium flow rate scale:

Among them: Qi check the flow table to select the large value of the water or air flow corresponding to a certain float number.
(4) Since the correction of viscosity is not considered in the calculation, it may be different from the result calculated by the factory.

2. Determination of correction coefficient K
(1) For liquid media
a. If Q is the liquid volume flow, calculate K by:

b. If Q is the liquid mass flow rate, calculate K by:

Where: ρf: selected float density (g/cm3)
Stainless steel float density is 7.8
Polytetrafluoroethylene float (PTFE) density is 3.4
Nickel alloy (Hasloy) density is 8.3
ρ: the density of the measured medium
(2) For gas medium
a. If Q is the volumetric flow rate of the gas under standard conditions (20 ° C, 0.1013 MPa), calculate K by the following formula:

b. If Q is the volumetric flow rate of the gas under operating conditions, calculate K by:

c. If Q is the mass flow rate of the gas, calculate K by:

In the above formula:
ρ: Density of the measured medium: density of the measured gas medium at 20 ° C, 0.1013 MPa (kg / m3)
P: absolute pressure of the gas medium to be measured (MPa)
T: absolute temperature of the measured gaseous medium (K)
Ρ0: density at 20 ° C, 0.1013 MPa (1.205 kg / m3)
P 0: absolute pressure of the calibration medium (0.1013MPa)
T 0: absolute temperature of the calibration medium (293.15K)

d, auxiliary density conversion formula

Where: ρst: density of the tested gaseous medium in the standard state (Kg/m3)
Ρt: density of the tested gas medium in operation (Kg/m3)
Tt: absolute temperature (K) of the measured gas medium under operating conditions
Pt: absolute pressure (MPa) of the tested gas medium under operating conditions
P0: absolute pressure (MPa) of the tested gas medium under standard conditions
T0: absolute temperature (K) of the tested gas medium under operating conditions

Structure

1. High temperature structure (G)
The high-temperature structure type (G type) is a flow measurement for a medium in which the temperature of the medium is too high or too low and the insulation of the measuring tube is required. The high temperature structure increases the distance between the measuring tube and the indicator to increase heat dissipation, increase the thickness of the insulating material, and ensure that the indicator works within the allowable ambient temperature range. The selection is "G" type.
Type G can measure the flow rate of media up to -80 °C - +300 °C.

2, structure with damper device (Z)
The damper configuration is used for media flow measurement when the flow meter inlet flow (pressure) is unstable, especially for gas measurement. Its structure is shown in the figure.

3, jacket type structure (T)
The jacketed structure is used for flow measurement of media that require heat or cooling (such as high viscosity and easy crystallization). The low boiling, low freezing point fluid is not vaporized and does not crystallize by heating or cooling the medium in the jacket.
For the introduction and export connection of heat-conducting medium, the standard type should use HG20594-97 DN15 PN1.6 flange. The other flange specifications can be marked with the manufacturer, and the pressure rating of the jacket is 1.6MPa.
See the FA standard flowmeter flange and external dimensions for the structure of the jacketed metal tube flowmeter .

4, high pressure type structure (Y type)
The high pressure type structure is used for flow measurement in which the measured medium pressure is greater than the standard pressure level. The high pressure type structure is shown below. At present, the high pressure of zui of FFM64 series can reach 32MPa. In addition, the high-pressure flowmeter is available with a built-in magnetic filter type with a mounting height of 350mm. FA, FB and FC type zui large pressure is 10MPa.

High-pressure form factor and weight

Note: 1, G is the weight of the instrument (kg)

Installation diagram

Installation considerations

In order to be able to work properly and achieve a certain measurement accuracy, the following points should be noted when installing the flowmeter:
· Must be mounted vertically on a vibration-free pipe. The fluid flows through the flowmeter from bottom to top, and the verticality is better than 2°, and the horizontal angle is better than 2° when installed horizontally;
· In order to facilitate the repair and replacement of the flowmeter and the cleaning of the measuring pipeline, the bypass piping and the bypass valve should be installed on the process pipeline;
· The inlet shall have a straight pipe section with a length of 5 times or more, and the outlet shall have a straight pipe section of 250 mm;
· If the medium contains ferromagnetic substances, a magnetic filter should be installed; if the medium contains solid impurities, consider adding a filter between the valve and the straight pipe section;
· When used for gas measurement, ensure that the pipeline pressure is not less than 5 times the pressure loss of the flowmeter to stabilize the float;
· In order to avoid the deformation of the flowmeter caused by the pipeline, the flange of the process pipeline must be coaxial with the flange of the flowmeter and parallel to each other. The pipeline supports to avoid the vibration of the pipeline and reduce the axial load of the flowmeter. The control valve in the measurement system Should be installed downstream of the flowmeter:
• When measuring gas, if the gas directly discharges the atmosphere at the outlet of the flowmeter, the valve should be installed at the outlet of the meter, otherwise a pressure drop will occur at the float and cause data distortion.
· When installing the PTFE-lined instrument, do not loosen the flange nut too tightly to avoid deformation of the PTEF liner;
· Instrument with liquid crystal display, try to avoid direct sunlight display, so as not to reduce the service life of liquid crystal; instruments with lithium battery power supply, try to avoid direct sunlight, high temperature environment (≥65 °C) to avoid reducing the capacity and life of lithium battery .

Fives, product model

Sixth, reference flow